Speech transmission over wireless radio-based LANs (Local Area Networks), such as IEEE 802.11 LANs, are currently implementing protocol enhancements in the MAC layer, which can allow better transport of time-sensitive traffic, like speech. These protocols frequently utilize reservation techniques to minimize loss of packets due to contention.
However, most wireless LAN modems are implemented with radio architectures which either do not offer space diversity (sampling of an electromagnetic wave at more than one point in space) or utilize only switched diversity (use of a second antenna when the primary is found to be in a “null”). As a consequence, these implementations may, even with a contention free MAC protocol, experience some packet loss.
Some types of radio communication systems, such as cellular, utilize special voice compression coding techniques which were designed to cope with packet loss due to propagation. In general, these coding techniques were designed for use with specific standards (e.g. ANSI-136, VSELP, GSM LPC-RPE, etc.). However, the trend today is to use packet radio systems to convey multimedia coding identical to that used in the wireline network (G.711 64 Kbps PCM, etc.). Such coders were designed to operate with error rates considerably below those normally experienced in radio environments. Accordingly, some exhibit audible impairments when subjected to substantial packet losses.
Since wireless LANs are now being contemplated as a means for voice transport as well as data transmission in enterprise, home, and public environments, it is important that users experience the same quality of service (QoS) as they would obtain with a wireline connection. Although combinational diversity (simultaneous sampling of an E-M wave at two or more points in space using separate receivers with intelligent algorithms to minimize error rate) combined with improved forward error correction (FEC) coding may become a feature of next-generation wireless LAN systems, the cost, size and power dissipation of such solutions currently makes them unattractive to consumers.
Accordingly, what is needed is a wireless LAN system and method that will allow voice and data transport and provide a high QoS, with a more reasonable cost, size and power dissipation than conventional systems and methods.